The present invention relates to the field of high pressure water systems and, more particularly, to a high pressure water system in a fire-fighting apparatus such as a fire engine.
A fire-fighting apparatus, such as a fire engine, requires a high pressure water system to provide sufficient force for projecting a stream of water from a fire hose a certain distance to the fire. These high pressure water systems usually operate at up to approximately 600 pounds per square inch (p.s.i.) of pressure. The pumper fire engine will normally include a centrifugal impeller pump for generating the high water pressure needed for fire-fighting. The fire engine""s high pressure water system will generally be connected to a low pressure source of water such as a fire hydrant, or even a no pressure source such as a pond. Multiple fire hoses are connected to the high pressure water system in the fire engine, and are used to discharge streams of water under relatively high pressure. The discharge pressure of a stream of water from such a fire hose is often sufficiently high that it requires more than one fire fighter to control the hose nozzle.
When fire fighters are finished extinguishing a fire, the pump in the fire engine is shut off and the hoses are left open until the pressure in the system drops to a relatively low level. The fire engine pump valves are then closed, and the fire hoses are disconnected from the fire engine water system. At this point, however, there usually remains some residual pressure in the fire engine""s water system, and this pressure should be released. The usual procedure is for an operator to open a manual pressure release valve located on the fire engine. Alternatively, the fire engine may be equipped with an automatically opening pressure release valve which will be self opening when water pressure in the line drops below a predetermined level, such as when fire fighters leave hose nozzles open to release pressure. There are times, however, when circumstances do not allow for the hoses to be left open for a sufficient time to release pressure, and pressure in the lines remains above the level required for an automatic valve to open. Further, manually operated valves must also be manually reset to their closed position before fire fighting operations resume, requiring operator intervention.
In view of the foregoing, the present invention advantageously provides a valve comprising both manual and automatic operation for releasing residual pressure in the fire engine""s high pressure water system would render several useful functions. During start up of the water pump, the valve would be opened manually to vent air from the high pressure water lines to help prevent cavitation, or the pump from losing its prime. Upon shutdown of the system and opening of the hose nozzles, the valve would open automatically when pressure dropped sufficiently, thus draining water remaining in the fire engine""s water system so as to help keep the fire engine""s interior lines clean. If fire hose nozzles cannot be left open to relieve pressure upon system shutdown, then the valve could be opened manually to relieve residual pressure so that the fire hoses can be safely disconnected, and to prevent the fireman disconnecting the hoses from being thoroughly drenched by water spraying under pressure when a hose connection is broken. The valve is additionally useful since it does not require manual reset to a closed position. when opened manually. The present valve, therefore, provides the advantages of opening automatically and manually, and of requiring no operator intervention to close the valve when opened manually.
The valve comprises a valve body having an inner cavity for water to flow therethrough. An inlet opening on the valve body is in fluid connection with the inner cavity to permit fluid flow thereinto. An outlet opening on the valve body is positioned in fluid connection with the inner cavity to permit fluid flow therefrom. A valve seat assembly is positioned in the inner cavity and comprises a first biasing member exerting a force against a valve plunger cooperating with a seal to thereby close the valve at or above a predetermined system pressure and substantially stop fluid flow through the outlet opening. The valve also includes an override comprising a manual activator having a second biasing member and a cooperating member positioned to transmit to said valve seat assembly a force applied by an operator, to thereby open the valve when pressure exceeds the predetermined system pressure.
The valve disclosed in the present invention is advantageously used in combination with a fire engine high pressure water system. Additionally, a high pressure water system having the disclosed valve is claimed as part of the invention. It should be understood, however, that the disclosed valve and method may be employed in any high pressure water system having similar requirements as that in a fire engine, and is not limited to just a fire engine""s high pressure water system.
The invention additionally discloses, in a high pressure water system having a water pump, a method of releasing residual pressure from the system. The method comprises shutting off the water pump, manually opening a first outlet connected to the high pressure water system until pressure drops to a predetermined level, and automatically opening a second outlet responsive to the predetermined pressure level to thereby release the residual pressure from the system.
In the method, a fire-fighting apparatus preferably comprises the high pressure water system, and the first outlet comprises a fire hose. In another embodiment of the method, the predetermined level of pressure is approximately 6 p.s.i. Also, the second outlet comprises a drain valve which opens responsive to a predetermined system pressure of approximately 6 p.s.i. or less. The method additionally provides that the drain valve may be opened manually above the predetermined system pressure.